1. Field of the Invention
The invention relates to a method for operating a sensor apparatus and to a sensor apparatus for a motor vehicle for coupling to a digital tachograph.
2. Related Art
U.S. Pat. No. 6,982,625 B2 discloses an event recorder for transmitting and storing electronic signature data. The event recorder is designed to be fitted to a vehicle and to transmit encrypted signatures and data. In the event of an accident or a traffic offense, an electronic fingerprint is thereby left behind and can be received by an external data acquisition device. The event recorder is integrated on a chip card arranged in a tamper-proof housing. The event recorder comprises a microcomputer, a memory, and a transmitter/receiver. A sensor is also provided for detecting sudden acceleration. Tampering with the event recorder can be detected by measuring physical forces on the event recorder and may result in the vehicle being immobilized.
DE 198 21 696 A1 discloses a method and an apparatus for transmitting and storing an item of information, in particular a distance covered by a motor vehicle, in a tamper-proof manner. The information is given by a number of temporally successive pulses. A counting unit counts arriving pulses. After predetermined periods of time in each case, the existing number of arrived pulses is transmitted to a receiver unit in a encrypted form according to an encryption algorithm. In the receiver unit, the number is decrypted according to the same encryption algorithm and the sum is determined and is stored. The counting unit contains a microprocessor with associated memory units and is connected to the receiver unit via a data line. The receiver unit contains a microprocessor and a memory. A pulse generator is connected to the counting unit in a tamper-proof manner.
DE 196 10 161 A1 discloses a data transmission apparatus in a vehicle including a pulse generator and a control device as well as a pulse generator for the control device. In addition to known transmission from the pulse generator to the control device, a signal generated by a sensor element is transmitted, on request by the control device, via a data line in encrypted form. In the control device, the signal transmitted in encrypted form is compared with the signal registered there and previously transmitted in a conventional manner. This comparison makes it possible to detect tampering on the transmission path. The pulse generator has a sensor element for detecting a rotational frequency of a transmission gearwheel and a signal conditioning circuit arrangement. The sensor element may be a Hall sensor element. The pulse generator or the control device has a monitoring function with a reset function. Initialization is provided with transmission of a key from the control device to the pulse generator.